Distorted sine wave displayed on labview

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Amalia Safiee

Joined Sep 21, 2017
9
Hello,

I am trying to develop a heart monitoring system using ECG. I just started this project and my current status is to display (on labview, through bluetooth transmission by arduino) a sine wave from a function generator. However, I am not sure why I seem to get discrete signals instead of a smooth sine wave.

upload_2017-10-13_14-31-33.png


upload_2017-10-13_14-32-32.png

What is the mistake here and how can I get the smooth sine wave?
 

wayneh

Joined Sep 9, 2010
16,102
This could be any of a number of causes. It could just be the charting method is using a zero value for time points in between the sampled points. Or, it looks a little like it's plotting a bar graph instead of a connect-the-dots line.

Or, it could be that the Arduino samples 'slowly' compared to the sine wave frequency. Try using a lower frequency so that you get more points per cycle. If possible, ask the Arduino to sample at a faster rate.

Or, the chart may not represent all the sampled data.
 

MrChips

Joined Oct 2, 2009
19,269
From what I can see, your ADC is a 10-bit ADC and the mid-point voltage of 2.5V gets converted to 512.
Hence your sine wave is being converted to values below and above 512.

Looks like your chart is showing a bar graph instead of connect-the- dots as wayneh points out.
 
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